In connection with certain types of fluid handling equipment or with certain processing operations which handle noxious materials and which necessitate fume venting, it is customary to have fume incinerator means in the venting lines to insure the substantial elimination of noxious fumes and the prevention of undesirable odors reaching neighboring areas. For example, in connection with sewage lift stations, particularly in the warmer southern states, there has been the use of small catalytic fume incinerator units to provide for a continuous treatment of the vented fumes from the enclosures over the lift station tanks and the accompanying pumps. However, at such times as the pumps may require inspection or repair there is the need to have substantially greater ventilation within the enclosure in order to permit workmen to enter and do work without the need of gas masks. As a result there is the need to have auxiliary fans and fume treatment means, unless there is to be pollution of the surrounding area. Additional catalytic or thermal incinerator means can, of course, be provided for this extra service; however, the extra expense of incinerator equipment and the frequent start-up procedures for such equipment can be burdensome.
It is thus an object of the present invention to provide for one or more beds of absorbent material and extra fan means to be used in effecting venting through the fume absorbing material. The motor and fan means need only be operated for those periods of time that workmen are to be in the enclosure or, alternatively, for periods of time where there may be an above normal generation and flow of noxious fumes in the processing chamber.
In an integrated venting system, it can also be an object of the invention to have automatic switch means to initiate the use of the auxiliary fan and the venting of fumes through the absorbent material, as well as automatic means to cut-off the fan operation and permit the fan unit of the incineration section to back-flush air through the absorbent material and effect the regeneration thereof. The switching can be, for example, responsive to the opening and closing of an access door to the enclosure being vented. Optionally, switching could be responsive to fluid levels in a chamber, fluid flow rates into and out of a given chamber, etc.
In one embodiment, the present invention provides a fume elimination and venting system for enclosures generating burnable and absorbable noxious fumes which provides for additional venting for controlled periods of time and will permit safe access to the interior of the enclosure, which comprises in combination: (a) at least one blower operated first venting means from the fume generating enclosure connecting with a fume incinerating means and the subsequent discharge of treated fumes and gases from the system, (b) additional vent means from said enclosure connective with at least one fume absorption section containing a gas pervious absorptive media, (c) auxiliary blower means connective with last said vent means and the absorption section providing for powered operated fume flow outwardly through te absorptive media and the resulting maintenance of a low level of residual noxious fumes within said enclosure for controlled periods of time, and (d) switch control means to cut on and off the auxiliary blower means for the additional vent means and effect the stoppage of the outward flow through the absorptive media and said auxiliary blower means whereby with a continuing venting through said first venting means and the fume incinerating means there is a resulting desorption of fumes from the absorptive media.
The fume incinerating means may be provided to operate thermally with suitable burner means being utilized to generate high temperature flame and gases which will, in turn, be suitable to oxidize the fumes from the collection zone and thus able to discharge less noxious treated fumes from the system. On the other hand, for purposes of economy, the system will typically utilize a gas pervious oxidizing catalyst material which will effect a lower temperature catalytic conversion and treating of the noxious fumes prior to their discharge from the system to the atmosphere. Various types of oxidizing catalysts can be utilized and it is not intended to limit the present system to any one type of catalyst. For example, an all metal catalyst prepared and used in the manner of the teaching of U.S. Pat. Nos. 2,658,742 and 2,720,494 can be particularly suitable. These patents teach the use of gas pervious mats of crinkled high temperature resistant alloy metal ribbons which in turn have been suitably treated or plated to have a highly active catalyst surface of a platinum group metal and, in particular, of a platinum or platinum and palladium. The base materials heretofore used for these types of all metal elements have typically been high nickel content alloys of various types such as Chromel, Nikrothal and Nickrome (which are the tradenames for, respectively, an alloy nickel and chromium, and an alloy of nickel, chromium and iron). The all metal catalyst mats may also be made of base materials which are nickel-free and are essentially of iron, chromium and aluminum. A suitable oxidizing catalyst embodying this type of base material is set forth in U.S. Pat. No. 3,867,313. It may also be noted that the suitable nickel-free ribbon is being presently marketed under the tradenames of Kanthal and Alkrothal, and that such ribbons may be coated with a platinum group metal or combinations of oxidizing metal components in the same manner as the heretofore indicated U.S. Pat. Nos. 2,658,742 and 2,720,494.
Still further, it is within the scope of the present invention to utilize a gas pervious bed of oxidizing catalyst which is of a non-metallic nature such as small spheres, cylinders, or pellets, as for example having an average dimension of the order of 1/16 inch to about 1/4 inch, of a refractory inorganic oxide suitably coated with an active oxidizing component. More particularly, the refractory base material may comprise alumina, silica-alumina, silica-alumina-zirconia, silica-thoria, silica-boria, and the like. The oxidizing agent which is utilized to impregnate the refractory inorganic oxide may comprise metals of Groups I, V, VI and VIII of the Periodic Table and, particularly, copper, silica, vanadium, chromia, iron, cobalt, nickel and platinum or palladium with the components being used singly or in combination with one or more active components. Gas pervious "honeycomb" types of refractory support members may also be coated with the aforementioned catalytic agents. The rigid refractory honeycomb supports will typically be made of compositions such as petalite, cordierite, spodumene, sillimanite, magnesium-silicates, alumino-silicates, zirconia, etc.
With regard to the auxiliary venting means to be connected with the fume enclosure and which will be brought into operation when it is desired to handle extra fume generation or necessary to have personnel enter the enclosure without the need of gas masks or other protective measures, it is desirable that there be adequate auxiliary vents to be used in connection with the catalyst or thermal incinerator means. Thus, it may be advisable to have two or more suitably spaced vent means connecting with the enclosure so as to insure suitable fresh air intake into the enclosure and safe working conditions while, at the same time, precluding noxious fumes being vented to the atmosphere. The type of absorbent to be used in connection with the auxiliary vent means will typically comprise gas pervious beds of carbon or activated carbon; however, in certain instances there may be utilized other fume absorbing agents such as alumina, activated alumina, silica gel types of materials, etc. In accordance with the present system, it is also necessary that the additional vent means be provided in a manner that there may be reverse flow therethrough, in other words, downwardly through the auxiliary blower means and an out-to-in flow with respect to the absorption bed such that the latter can be desorbed and, in effect, regenerated after personnel leave the enclosure and auxiliary blower means are turned off. As heretofore noted, the desorbed fumes from the absorption beds of the additional vent means will be drawn downwardly into the enclosure and thence through the catalytic or thermal incinerator means to be purified. Thus each absorption bed is regenerated for reuse at a next controlled period of time.